Free Energy of Membrane Protein Unfolding Derived from Single-Molecule Force Measurements

Preiner, Johannes; Janovjak, Harald; Rankl, Christian; Knaus, Helene; Cisneros, David A.; Kedrov, Alexej; Kienberger, Ferry; Müller, Daniel J.; Hinterdorfer, Peter

doi:10.1529/biophysj.106.096982

Cited by 44 publications

(53 citation statements)

References 48 publications

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“…In other words, it should be in the stalk region or transmembrane helix of GPIba. The force required to unfold a transmembrane helix is much stronger (.100 pN) 42,43 than what was observed here (;10 pN). In addition, unfolding of the 25-residue transmembrane helix of GPIba would have produced an unfolding contour length of ;10 nm, much shorter than .20 nm observed in the force curves ( Figure 2C).…”

Section: Localization Of Msd To the Stalk Region Of Gpibacontrasting

confidence: 55%

Identification of a juxtamembrane mechanosensitive domain in the platelet mechanosensor glycoprotein Ib-IX complex

Zhang

Deng

Zhou

et al. 2015

Blood

160

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Section: Localization Of Msd To the Stalk Region Of Gpibacontrasting

confidence: 55%

Identification of a juxtamembrane mechanosensitive domain in the platelet mechanosensor glycoprotein Ib-IX complex

Zhang

Deng

Zhou

et al. 2015

Blood

160

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“…[85][86][87] By applying Jarzynski's equality it was found that the equilibrium folding and insertion energies of the membrane proteins range from % 160 kcal mol À1 (for bacteriorhodopsin and halorhodopsin) to % 280 kcal mol À1 (for NhaA). [88] As expected for equilibrium properties, these energies are force-loading rate-independent, that is, they do not depend on how far from equilibrium the experiment was performed. Remarkably, the average free energy for unfolding and extracting single amino acids is essentially the same for all three membrane proteins (%0.70 kcal mol…”

Section: Determining Insertion and Folding Energies By Using Jarzynskmentioning

confidence: 57%

“…A sequence-dependent comparison with the biophysical and biological hydrophobicity scales introduced by White and Wimley [89] and Hessa et al [90] indicate that these energies contain hydrophobic interactions and contributions from hydrogen bonds. [88] Additionally, the Jarzynski analysis reveals heterogeneous energetic properties of individual transmembrane a-helices and a-helical segments. The unfolding pathways of halorhodopsin resemble those of bacteriorhodopsin except for one difference-halorhodopsin exhibits an additional pi-bulk interaction that splits its a-helix E into two structurally distinct segments.…”

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confidence: 99%

From Valleys to Ridges: Exploring the Dynamic Energy Landscape of Single Membrane Proteins

et al. 2008

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Membrane proteins are involved in essential biological processes such as energy conversion, signal transduction, solute transport and secretion. All biological processes, also those involving membrane proteins, are steered by molecular interactions. Molecular interactions guide the folding and stability of membrane proteins, determine their assembly, switch their functional states or mediate signal transduction. The sequential steps of molecular interactions driving these processes can be described by dynamic energy landscapes. The conceptual energy landscape allows to follow the complex reaction pathways of membrane proteins while its modifications describe why and how pathways are changed. Single-molecule force spectroscopy (SMFS) detects, quantifies and locates interactions within and between membrane proteins. SMFS helps to determine how these interactions change with temperature, point mutations, oligomerization and the functional states of membrane proteins. Applied in different modes, SMFS explores the co-existence and population of reaction pathways in the energy landscape of the protein and thus reveals detailed insights into local mechanisms, determining its structural and functional relationships. Here we review how SMFS extracts the defining parameters of an energy landscape such as the barrier position, reaction kinetics and roughness with high precision.

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“…unfolding of 90 k B T or 53 kcal·mol −1 was derived, similar to helix-hairpins in bacteriorhodopsin (29). Certainly this solidity constitutes a prerequisite for holding the pigments precisely in space for light-harvesting function.…”

Section: Resultsmentioning

confidence: 83%

Forces guiding assembly of light-harvesting complex 2 in native membranes

Liu

Duquesne

Oesterhelt

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Interaction forces of membrane protein subunits are of importance in their structure, assembly, membrane insertion, and function. In biological membranes, and in the photosynthetic apparatus as a paradigm, membrane proteins fulfill their function by ensemble actions integrating a tight assembly of several proteins. In the bacterial photosynthetic apparatus light-harvesting complexes 2 (LH2) transfer light energy to neighboring tightly associated core complexes, constituted of light-harvesting complexes 1 (LH1) and reaction centers (RC). While the architecture of the photosynthetic unit has been described, the forces and energies assuring the structural and functional integrity of LH2, the assembly of LH2 complexes, and how LH2 interact with the other proteins in the supramolecular architecture are still unknown. Here we investigate the molecular forces of the bacterial LH2 within the native photosynthetic membrane using atomic force microscopy single-molecule imaging and force measurement in combination. The binding between LH2 subunits is fairly weak, of the order of k B T , indicating the importance of LH2 ring architecture. In contrast LH2 subunits are solid with a free energy difference of 90 k B T between folded and unfolded states. Subunit α-helices unfold either in one-step, α-and β-polypeptides unfold together, or sequentially. The unfolding force of transmembrane helices is approximately 150 pN. In the two-step unfolding process, the β-polypeptide is stabilized by the molecular environment in the membrane. Hence, intermolecular forces influence the structural and functional integrity of LH2.atomic force microscopy | photosynthesis | protein unfolding | membrane protein assembly M embrane protein function is intimately linked and influenced by its structural integrity and molecular environment (1-3). Photosynthesis is a paradigm of such orchestrated molecular action, for which the implicated proteins have evolved to form supramolecular assemblies (4). Knowledge of supramolecular architecture and interaction forces and energies are indispensable for a complete understanding of a membrane protein structure and function.The atomic force microscope (AFM) (5) can be used as a high-resolution imaging (6) and as a force-measurement tool (7). Most elegantly the two applications were combined allowing the attribution of structural changes to force events (8). More recently, the AFM has proven the unique tool for studying the supramolecular assembly of the bacterial photosynthetic unit (9-12) and has provided a solid basis for the understanding of the ensemble function of the photosynthetic proteins (4, 13-15).The light-harvesting process in photosynthetic bacteria starts with photon capture at the peripheral light-harvesting complex 2 (LH2) that transfers the absorbed excitation energy to the light-harvesting complex 1 (LH1) associated with the reaction center (RC). The LH2 structure is well described by X-ray crystallography (16, 17) and AFM in native membranes (12,(18)(19)(20). Typically, the LH2 complexes appe...

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Free Energy of Membrane Protein Unfolding Derived from Single-Molecule Force Measurements

Cited by 44 publications

References 48 publications

Identification of a juxtamembrane mechanosensitive domain in the platelet mechanosensor glycoprotein Ib-IX complex

Identification of a juxtamembrane mechanosensitive domain in the platelet mechanosensor glycoprotein Ib-IX complex

From Valleys to Ridges: Exploring the Dynamic Energy Landscape of Single Membrane Proteins

Forces guiding assembly of light-harvesting complex 2 in native membranes

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